Spinal plate and drill guide

ABSTRACT

Bone plates and bone plate systems are provided in which a bone plate includes a plurality of bone screw holes formed therein and positioned in laterally adjacent pairs. Positioned between the laterally adjacent pairs of bone screw holes are stabilizing strut. The bone plate system can additionally include windows positioned between longitudinally adjacent struts. Transverse bone screw planes can extend across the superior and inferior edges of the bone screw holes and define the minimum longitudinal boundaries of the windows. A guide device adapted for mating with the bone plate is also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This Application is a continuation of U.S. application Ser. No.11/371,741 filed Mar. 9, 2006 and entitled “Spinal Plate and DrillGuide,” which claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 60/749,642 filed Dec. 9, 2005 and entitled “SpinalPlate and Drill Guide,” which are each hereby incorporated herein byreference in their entirety.

BACKGROUND

For a number of known reasons, bone fixation devices are useful forpromoting proper healing of injured or damaged vertebral bone segmentscaused by trauma, tumor growth, or degenerative disc disease. Thefixation devices immobilize the injured bone segments to ensure theproper growth of new osseous tissue between the damaged segments. Thesetypes of bone fixation devices often include internal bracing andinstrumentation to stabilize the spinal column to facilitate theefficient healing of the damaged area without deformity or instability,while minimizing any immobilization and post-operative care of thepatient.

One such device is an osteosynthesis plate, more commonly referred to asa bone fixation plate, that can be used to immobilize adjacent skeletalparts such as bones. Typically, the fixation plate is a rigid metal orpolymeric plate positioned to span bones or bone segments that requireimmobilization with respect to one another. The plate is fastened to therespective bones, usually with bone screws, so that the plate remains incontact with the bones and fixes them in a desired position. Bone platescan be useful in providing the mechanical support necessary to keepvertebral bodies in proper position and bridge a weakened or diseasedarea such as when a disc, vertebral body or fragment has been removed.

Such plates have been used to immobilize a variety of bones, includingvertebral bodies of the spine. These bone plate systems usually includea bone plate having a plurality of screw openings. The openings areeither holes or slots to allow for freedom of screw movement. The boneplate is placed against the damaged vertebral bodies and bone screws areused to secure the bone plate to the spine, usually with the bone screwsbeing driven into the vertebral bodies. Exemplary systems are describedin U.S. Pat. Nos. 6,159,213 to Rogozinski; 6,017,345 to Richelsoph;5,676,666 to Oxland et al.; 5,616,144 to Yapp et al.; 5,549,612 to Yappet al.; 5,261,910 to Warden et al.; and 4,696,290 to Steffee.

Despite the existence of these bone plate systems, there remains a needfor a bone plate system that can provide increased visualization of asurgical site to facilitate alignment and implantation of bone plate,while providing sufficient strength and rigidity to immobilize the boneto which it is implanted.

SUMMARY

Disclosed herein are bone plate systems including a bone plate having aunique geometry that renders the plate effective and convenient toinstall. In spinal plate applications, for example, the plate providesfor enhanced visibility of the interface between the disc or implant andvertebral bodies and can also provide enhanced visibility of thevertebral bodies.

In one embodiment, an implantable bone plate is provided. The bone platehas a longitudinal axis extending from a superior end to an inferior endand a plurality of bone screw holes. The bone screw holes can be alignedin the plate in laterally adjacent pairs, wherein each laterallyadjacent pair of bone screw holes has a stabilizing strut extendingbetween each laterally adjacent bone screw hole of the pair. Inaddition, each of the laterally adjacent pairs of bone screw holes candefine a transverse plane (i.e., a “transverse bone screw hole plane”)extending between an edge of each laterally adjacent bone screw hole ofthe pair. The plate further includes a window formed in the plate andextending longitudinally between the laterally adjacent pairs of bonescrew holes. At one end, the window can have a superior boundary thatextends at least to the transverse bone screw hole plane of a firstlaterally adjacent pair of bone screw holes. In one aspect, the windowalso includes an inferior boundary that extends at least to thetransverse bone screw hole plane of a second laterally adjacent pair ofbone screw holes that is spaced longitudinally from the first adjacentpair of bone screw holes.

In one aspect, the bone plate is a two level plate and comprises twowindows and three pairs of laterally adjacent bone screw holes.Alternatively, the bone plate could be a single level plate or a three(or more) level plate.

In another aspect, the bone plate window extends longitudinally beyondat least one of the superior boundary and inferior boundary of atransverse bone screw hole plane. The bone plate window can have avariety of shapes and sizes and can, for example, extend longitudinallyand transversely.

To facilitate mating of the plate to a surgical tool, the bone plate caninclude recessed areas at the superior and inferior ends of the plate.For example, the recessed areas can be positioned at the inferior andsuperior ends of the plate. The bone plate can also include a bone screwlocking mechanism. In one aspect, the bone screw locking mechanismcomprises a rotatable cam integrated with the plate.

In another embodiment, an implantable bone plate system is provided. Thesystem includes an implantable bone plate and a drill guide adapted tomate with the bone plate. The bone plate can include a plate body havinga longitudinal axis and a plurality of bone screw holes. The bone screwholes can be aligned in the plate in laterally adjacent pairs, whereineach laterally adjacent pair of bone screw holes has a stabilizing strutextending between each laterally adjacent bone screw hole of the pair.In addition, each of the laterally adjacent pairs of bone screw holescan define a transverse bone screw plane extending between an edge ofeach laterally adjacent bone screw hole of the pair. The plate canfurther include at least one window having a superior boundary thatextends at least to the transverse bone screw hole plane of a firstlaterally adjacent pair of bone screw holes and an inferior boundarythat extends at least to the transverse bone screw hole plane of asecond laterally adjacent pair of bone screw holes that is spacedlongitudinally from the first adjacent pair of bone screw holes.

The system also includes a guide device adapted for use with the boneplate. In one aspect, the guide device comprises a guide barrel and atleast one feature extending from a distal end of the guide barrel. Theguide device can be adapted to register with a sidewall of the windowand an outer sidewall of the plate body.

In one aspect, the at least one feature of the guide device includefirst, second, and third features. The first feature can be adapted tomate with a recessed portion of the plate body sidewall, the secondfeature can be adapted to mate with another portion of the plate bodyouter sidewall, and the third feature can be adapted to mate with aninner side wall of the window.

In another aspect, the at least one feature of the guide device includesmultiple tabs. The tabs can be spaced to receive a portion of the boneplate therebetween. For example, at least one of the tabs can be adaptedto be positioned against the sidewall of the window and at least one ofthe tabs is adapted to be positioned against the outer sidewall of thebone plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a prior art fixation device mounted on a spinal column;

FIG. 2 is a front view of one embodiment of an implantable bone plate,as described herein, positioned on a spinal column;

FIG. 3 illustrates another embodiment of the implantable bone platedescribed herein;

FIG. 4 illustrates yet another embodiment of the implantable bone platedescribed herein;

FIG. 5A illustrates a perspective view of one embodiment of a bone screwfor use with the bone plate described herein

FIG. 5B illustrates a cross sectional view of the bone screw of FIG. 5A;

FIG. 5C is a perspective view of yet another bone screw includes alocking mechanism;

FIG. 6A is a sectional, top view of a bone screw and a bone screwlocking mechanism;

FIG. 6B is a top view of the locking mechanism of FIG. 6A rotated 45°;

FIG. 6C is a top view of the locking mechanism of FIG. 6A rotated 90°;

FIG. 6D is a top view of the locking mechanism of FIG. 6A rotated 180°;

FIG. 7A is a perspective view of one embodiment of a bone plate systemdescribed herein;

FIG. 7B is another perspective view of the bone plate system of FIG. 7A;

FIG. 7C is a bottom view of the bone plate system of FIG. 7A;

FIG. 8A is a perspective view of another embodiment of a bone platesystem described herein;

FIG. 8B is another perspective view of the bone plate system of FIG. 8A;and

FIG. 8C is a bottom view of the bone plate system of FIG. 8A.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The following exemplary embodiments are described herein with referenceto bone plates used to span and immobilize adjacent vertebral bodies inspinal fixation techniques. However, it is understood that the boneplate systems described herein may be applicable to the fixation of anytype of adjacent bones or bone segments. In addition, one skilled in theart will appreciate that while plate 10 is described as being fixed tobone, the term “bone” is used broadly and includes applications in whicha layer of soft tissue is covering all or a portion of the hard tissuesurface.

In one embodiment, disclosed herein is a bone plate including a platebody that extends along a longitudinal axis and has a plurality ofapertures defining bone screw holes for receiving bone screws. The platebody can also include stabilizing struts and a viewing window. Forexample, in one aspect, at least some of the bone screw holes arepositioned in laterally adjacent pairs, the laterally adjacent pairs ofbone screw holes being spaced longitudinally from each other. Extendingbetween the laterally adjacent pairs of bone screws are struts thatprovide rigidity to the plate. Openings in the plate, positioned betweenthe struts, can provide a viewing window that enhances visibility of animplant, disc, and/or vertebral body (midline and/or endplate).

The plate illustrated and described in the exemplary embodiments isparticularly well suited for placement on the spine. The plate can be inthe form of a single level plate, which spans two adjacent vertebralbodies, or a multilevel plate that spans three or more adjacentvertebral bodies.

FIG. 1 illustrates a previously known bone plate 1 having a plurality ofbone screw holes 2 and fixation pin-receiving holes 6. Conventional boneplates, such as bone plate 1, provide somewhat limited visibility of thevertebrae due to substantially closed regions 4 that extend aroundlaterally opposed bone screw holes 2. As a result, visualization windows5, disposed between closed regions 4, provide limited visibility ofvertebral bodies 7 and the disc/vertebral body interface. While windows5 allow some visibility of the intervertebral space, the expansivenature closed regions 4 can make plate positioning and implantinspection more difficult. In contrast, disclosed herein is plate 10which, as illustrated in FIG. 2 mounted upon an anterior cervicalsurface of a spine, has open areas 32 a, 32 b that have dimensions and aconfiguration that provides enhanced visualization of the vertebralbodies 7 a, 7 b, 7 c on which the plate is to be mounted and of thedisc/vertebral body interface. In addition, plate 10 includes transversestruts that provide sufficient plate rigidity, while having a smallprofile that maximizes visibility.

FIGS. 2 through 4 illustrate one exemplary embodiment of bone plate 10as disclosed herein. With respect to FIG. 2, bone plate 10 includes aplate body 12 that extends longitudinally along axis L from a superiorend 24 to an inferior end 26 and that is sized and shaped forpositioning on vertebral bodies. The plate body has a bone contactingsurface (not shown) and an opposed, non-bone contacting surface 22.Further, body 12 has outer sidewalls 28 a, 28 b, which define the outeredge of the plate, and inner sidewalls 30 a, 30 b (defining open area 32b discussed below), which are opposed to one another. Positioned onplate body 12 are a plurality of bone screw holes 14 a, 14 b, 14 c, 14d, 14 e, 14 f, (FIG. 3) and stabilizing struts 20 (FIG. 3). The openareas 32 a, 32 b, as noted above, are positioned between struts 20.

Bone plate 10, as illustrated in FIGS. 2 through 4, includes a widththat varies along the longitudinal axis of the plate. The outersidewalls 28 a, 28 b, can be substantially linear, except adjacent tobone screw holes 14 a through 14 f where they are somewhat curved asdiscussed below. The shape of outer sidewalls 28 a, 28 b can provideadditional width of the plate as measured across the bone screw holeswhile minimizing the plate size adjacent to windows 32 a, 32 b. Theshape of the bone plate can also facilitate mating with a guide deviceas explained below.

In one aspect, the outer and inner sidewalls of the plate surroundingbone screw holes 14 have a curved shape. In particular, the outer andinner sidewalls adjacent bone screw holes 14 at superior 24 and inferior26 ends of the plate can follow a curvature that matches at least aportion of the curvature of an inner wall 38 (FIG. 4) that defines thebone screw holes 14. The outer sidewall of the bone plate adjacent thebone screw holes at the superior 24 and inferior 26 ends of the platethus can follow a curvature that is at least partially circular.

In addition, the superior and inferior ends 24, 26 of plate body 12 canhave recessed regions 31 a, 31 b (FIG. 4). In one embodiment, inaddition to minimizing the profile of plate body 12, recessed regions 31a, 31 b facilitate mating of plate 10 with a surgical tool as discussedbelow.

Outer sidewall 28 a, 28 b adjacent to the bone screw holes 14 b, 14 e inthe middle portion of the plate can also be curved. For example, theplate sidewall adjacent to bone screw holes 14 b, 14 e can curve outwardto accommodate the diameter of bone screw holes 14 b, 14 e. In oneaspect, the curved portions of plate body 12 adjacent to bone screwholes 14 a, 14 e are complementary to a corresponding segment of innerwall 38 of the bone screw holes.

Bone plate 10 disclosed herein can have features that facilitatemounting of bone plate 10 on a vertebral column, such as, for example, apreformed curvature that is complementary to the vertebrae upon whichthe plate is to be mounted. For example, the bone-contacting surface ofthe exemplary plate 10 can have a longitudinal curve X (FIG. 3) thatapproximates the lordotic curvature of the vertebrae upon which theplate is to be mounted. For example, the plate can have a longitudinalcurve X that extends in the sagital plane (i.e., in thesuperior-inferior direction) and that has constant radius along thelength of the plate 10. Alternatively, the plate 10 may comprise aplurality of longitudinal segments that are configured to collectivelyprovide the plate with a longitudinal curvature that approximates thelordotic curvature of the vertebrae. For example, one or more of thelongitudinal segments may have a longitudinal curvature or may beoriented at angle relative to the other longitudinal segments.

While the exemplary plate 10 may be curved only along longitudinal axisL, in another embodiment, plate 10 can also include a transverse curve Y(FIG. 3) that approximates the transverse curvature of the vertebraeupon which the plate is to be mounted. The plate 10 may have atransverse curvature along the length of the plate 10 or along discretelongitudinal segments of the plate. For example, the middle portion ofthe exemplary plate 10 may have a transverse curvature that approximatesthe transverse curvature of the vertebrae. Alternatively, the superiorend 24 and/or the inferior end 26 may have a different transversecurvature.

The bone plate, as mention above, further includes a plurality of bonescrew holes 14 formed along the bone plate and extending through theplate from the non-bone contacting surface 22 to the bone contactingsurface. In addition, plate body 12 can include locking mechanisms 35(FIG. 2) adapted to lock bone screws in bone screw holes.

In one aspect, the bone screw holes are positioned in laterally adjacentpairs. For example, a first bone screw hole in each pair can bepositioned along longitudinal axes l₁, and a second bone screw hole ineach pair can be positioned along longitudinal axis l₂. In addition, asshown in FIG. 4, the bone screw hole pairs are spaced longitudinallysuch that longitudinally adjacent bone screw holes (e.g., holes 14 a, 14b and 14 b, 14 c) will be positioned on different vertebral bodies whenthe bone plate is implanted within a patient. In the embodimentsillustrated in FIGS. 2 trough 4, bone plate 10 is a two level platehaving three bone screw hole pairs, each pair of bone screw holescorresponding to a different vertebral body 7 a, 7 b, 7 c. Other typesof plates are also contemplated, including, for example, a single levelplate having two pairs of opposed bone screw holes. In addition, otherplates, such as three or more level plates are also contemplated.

Plate body 12 can further include at least one strut 20 that extendstransversely between laterally adjacent bone screw holes. In one aspect,struts are positioned between each pair of laterally adjacent bonescrews to provide support to plate 10. When bone plate 10 is implanted,the area of plate body 12 adjacent to bone screw holes 14 is subject tostress. Struts 20 can support plate 10 in these high stress areas andprovide plate rigidity.

However, unlike conventional bone plates which have a large closedregion around bone screw holes, struts 20 have a minimum profile andthus are adapted to provide maximum visibility. In particular, plate 10can include an open space that extends between struts 20, and in oneembodiment open spaces 32 a, 32 b extend longitudinally between eachadjacent strut 20. The open spaces 32 a, 32 b, as noted above, provideenhanced visibility of the vertebral bodies onto which plate 10 is to bemounted. In particular, the open spaces 32 a, 32 b can be useful toensure proper alignment of the plate on the vertebral bodies. Forexample, the open spaces can allow a partial midline view of thevertebrae to facilitate a midline alignment of plate 10 on the vertebralbodies. In addition, the open spaces can allow inspection of theintersection of vertebral body 7 and an implant or disc.

In one aspect, at least one end of the open spaces can extend at leastto a transverse bone-screw-hole plane defined by the edges of laterallyadjacent bone screw pairs. As shown in FIG. 4, the inferior edges ofbone screw holes 14 a, 14 d define a transverse plane T₁ and thesuperior ends of bone screw holes 14 b, 14 e define a transverse planeT₂. Window 32 a can extend at least from transverse plane T₁ to at leasttransverse plane T₂. Similarly, window 32 b can extend between atransverse plane T₃ and a transverse plane T₄ defined by the inferioredges of bone screw holes 14 b, 14 e and by the superior edges of bonescrew holes 14 c, 14 f, respectively.

The recessed areas 31 a, 31 b at the superior and inferior ends 24, 26of plate body 12 can similarly extend to a transverse plane defined bythe edges of bone screw holes 14 a, 14 c, 14 d, 14 f. For example, thesuperior ends of bone screw holes 14 a, 14 d can define a transverseplane T₅ and the inferior ends of bone screw holes 14 c, 14 f can definea transverse plane T₆. Recessed area 31 a, can extend toward theinferior end of plate body 12 to transverse plane T₅, and recessed area31 b can extend toward the superior end of plate body 12 to transverseplane T₆.

In another embodiment, window 32 a, window 32 b, and/or recessed areas31 a, 31 b can extend beyond transverse planes T₁, T₂, T₃, T₄, T₅, T₆.For example, in FIG. 4, the inferior end of window 32 a extends beyondtransverse plate T₂, while the superior end of window 32 a does not. Thechoice of how far to extend windows 32 a, 32 b can depend, for example,on the placement of an implant and/or the need to view a particularportion of the anatomy.

Windows 32 a, 32 b can have a variety of shapes and sizes. In oneembodiment, windows 32 a, 32 b extend transversely as shown in FIG. 2.For example, the mid portion of windows 32 a, 32 b can extendtransversely toward the sidewalls 28 a, 28 b of plate body 12 and definewindows having generally “plus” shapes. The “plus” shaped windows areone example of a window shape that can provide a maximum viewing areawhile allowing enough space on plate body 12 for locking mechanisms 35.One skilled in the art will appreciate that windows 32 a, 32 b can havea variety of other shapes such as oval, round, rectangular, triangular,and irregular. In addition, windows 32 a, 32 b can each have differentshapes.

In addition, while a single strut is illustrated for each pair oflaterally adjacent bone screw holes and a single window extends betweenadjacent struts, plate body 12 can include additional struts (not shown)and additional windows (not shown) at any point along the length of theplate. In one embodiment, plate body 12 can include more than a singlewindow between each adjacent strut. For example, side-by-side windowscould be positioned between adjacent struts. Alternatively, plate body12 could include additional struts (i.e., more struts than pairs oflaterally adjacent bone screw holes) and additional windows between theadditional struts. In yet another embodiment, plate body 12 couldinclude fewer struts (and windows) than the number of laterally adjacentpairs of bone screw holes.

In another embodiment, a bone plate system, including bone plate 10 andbone screws 13, is disclosed. FIGS. 5A and 5B illustrate an exemplarybone screw 13 that has a proximal head portion 40 and a distal threadedshank 42. Head 40 can be shaped and dimensioned to sit within bone screwhole 14 when implanted into bone to fix bone plate 10 in position. Oneskilled in the art will that bone screw 13 is exemplary and that avariety of other bone screws or other fixation devices can be used withthe bone plate system.

Once bone screw 13 is implanted through bone plate 10, a surgeon canlock the bone screws to bone plate 10 to prevent screw backout. Forexample, the various embodiments of the spinal plates disclosed hereincan include a locking or retaining mechanism for locking the bone screwto the bone plate and preventing bone screw backout. In one embodiment,the locking mechanism can be integrated into the screw head, asdescribed in a U.S. patent application Ser. No.: 10/904,992, entitled“Locking Bone Screw and Spinal Plate System” of Gorhan et al., which isincorporated by reference herein in its entirety. For example, FIG. 5Cillustrates bone screw 13′ with an integrated locking cam 43 rotatablypositioned within bone screw head 40. In use, bone screw 13′ can beseated in bone screw holes 14 and the locking cam 43 can be rotated toprovide bone screw backout resistance.

In another embodiment, the locking mechanism can be integrated onto thesurface of the plate. The integrated locking mechanism can be, forexample, a cam that is rotatable between an unlocked position and alocked position, in which the cam is forced against the head of the bonescrew to provide bone screw backout resistance. For example, FIGS. 6Athrough 6D illustrate cam 44 rotatably positioned adjacent to bone screw13 in bone screw hole 14 of bone plate 10. Other exemplary cam-typelocking mechanisms are described in U.S. Pat. No. 5,549,612 of Yapp etal. entitled “Osteosynthesis Plate System,” which is also incorporatedby reference herein in its entirety. Other exemplary retaining orlocking mechanisms include, by way of non-limiting example, lockingwashers, locking screws, and bone screw covers. One skilled in the artwill appreciate that various combinations of locking mechanisms can beused as well. Other exemplary locking mechanisms are disclosed in U.S.Pat. Nos. 6,331,179 to Fried et al., 6,159,213 to Rogozinski; 6,017,345to Richelsoph; 5,676,666 to Oxland et al.; 5,616,144 to Yapp et al.;5,261,910 to Warden et al.; and 4,696,290 to Steffee.

It is understood that the bone plate system may include different typesof bone screws having varying functionalities. For example, the bonescrews can be of a rigid type in which after a screw locking mechanismis engaged, movement of the screw in any direction is prevented. Thebone screws can also be of a semi-rigid type in which after a screwlocking mechanism is engaged, screw backout is prevented, but the screwis able to move in all directions (i.e., polyaxially). Further, the bonescrews can also be of a hybrid type in which after a screw lockingmechanism is engaged, screw backout is prevented, but the screw is ableto move in only one selected direction (e.g., the superior-inferior orthe transverse direction). Moreover, the bone screws may translatewithin an aperture of a plate. For example, a bone screw may translatealong the length of an elongated slot defining an aperture in the plate.One skilled in the art will appreciate that a bone plate system may beprovided having any single screw type or a combination of all or any ofthe screw types.

The bone plate system can also include a surgical tool such as, forexample, a guide device 50 adapted to mate with bone plate 10 inregistration with bone screw holes 14. An exemplary guide device 50 isshown in FIGS. 7A and 7B. Guide device 50 generally includes an elongateshaft 52 having a proximal handle portion (not shown) and a distal endcoupled to a guide member 56. The shaft 52 may be offset from, andangled with respect to, guide member 56, as shown in FIGS. 7A and 7B.Guide member 56 includes a least one pathway 60 extending therethroughwith one or more alignment members 62 extending from a distal portionthereof. Alignment members 62 can be spaced apart such that they areadapted to engage and/or align with a portion of the bone plate adjacentto and external of bone screw holes 14.

In one embodiment, pathway 60 is sized (i.e., in diameter) and shaped toallow the passage of a variety of bone preparation surgical tools (e.g.,drill, tap, etc.) and bone screws 13 through pathway 60 and into bonebeneath bone plate 10. In use, alignment members 62 are positionedexternal to bone screw hole 14 to position pathway 60 in registrationwith a bone screw hole. Once registration is achieved, the bone beneathbone plate 10 can be prepared (e.g., drilling, tapping, etc.), and bonescrews subsequently can be implanted into the prepared bone throughpathway 60 without removing guide device 50.

Alignment elements 62 can include four tabs 62′ (best seen in FIG. 7C)adapted to engage the outer sidewalls of bone plate 12 adjacent to thebone screw holes and the inner sidewall(s) 30 a, 30 b of open area 32.The tabs can be shaped to match the curved profile of the sidewallsadjacent to the bone screw holes. For example, a guide device adapted toregister with the bone screw holes in the plate illustrated in FIGS. 2through 4 would have tabs 62′ adapted to match recessed area 31 a (31 b)on one side of one of the struts strut 20, open area 32 on the otherside of the strut, and the outer sidewall 28 a, 28 b of the plateadjacent to the bone screw hole. In one aspect, the relative dimensionsof the space between tabs 62′ and the width of the plate adjacent bonescrew holes can be such that guide device 50 achieves an interferencefit with plate body 12. Such an interference fit would enable the guidedevice 50 to engage the plate in a manner that enables it to function asa plate holder. One skilled in the art will appreciate the shape andspacing of tabs 62′ can also be adapted to form a variety of other fitswith bone plate 10, such as a sliding clearance fit.

In one embodiment, guide device 50 is a single barrel device adapted toregister with a single bone screw hole and having a single pathway 60through the guide member 56 as shown in FIGS. 7A and 7B. In anotherembodiment, illustrated in FIGS. 8A, 8B, and 8C a guide device 50′ couldinclude multiple pathways for registering with multiple bone screw holes14 at the same time. For example, the multiple pathways can be spacedsuch that when the guide device is mated to bone plate 10, the pathwaysregister with two or more bone screw holes 14. One such exemplary guidedevice is disclosed in application Ser. No. 10/776,414, entitled “GuideFor Spinal Tools, Implants, and Devices,” filed Feb. 11, 2004 andincorporated hereby reference in its entirety. The alignment elements onthe dual pathway guide device can similarly include two tabs that extendfrom the distal portion of the single guide member. In use, tabs 62′ canmate with the outer sidewall 28 a, 28 b of plate body (and span opposedbone screw holes), recessed areas 31 a, 31 b, and/or open area 32.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1-19. (canceled)
 20. An implantable bone plate, comprising: an elongateplate having first and second parallel longitudinal axes; a plurality ofbone screw holes, the bone screw holes being aligned on the first andsecond longitudinal axes in laterally adjacent pairs; a plurality ofrotatable cams each being disposed adjacent to a respective one of theplurality of bone screw holes, each cam being rotatable between anunlocked position and a locked position; and a window formed in theplate and extending longitudinally between the laterally adjacent pairsof bone screw holes, the window having: a superior portion defined byopposed lateral sidewalls and a superior sidewall, the superior portionbeing at least partially disposed between first and second cams of theplurality of cams, an inferior portion defined by opposed lateralsidewalls and an inferior sidewall, and a mid-portion extending betweenthe superior and inferior portions, the mid-portion having a widthextending between opposed lateral sidewalls that is greater than a widthextending between the opposed lateral sidewalls of the superior andinferior portions.
 21. The bone plate of claim 20, wherein the lateralsidewalls of the inferior portion of the window are parallel and thelateral sidewalls of the superior portion of the window are parallel.22. The bone plate of claim 20, wherein each laterally adjacent pair ofbone screw holes has a stabilizing strut extending between eachlaterally adjacent bone screw hole of the pair.
 23. The bone plate ofclaim 20, wherein: each of the laterally adjacent pairs of bone screwholes has a transverse bone screw plane extending between an edge ofeach laterally adjacent bone screw hole of the pair; the superiorsidewall of the superior portion of the window extends at least to thetransverse bone screw hole plane of a first laterally adjacent pair ofbone screw holes; and the inferior sidewall of the inferior portion ofthe window extends at least to the transverse bone screw hole plane of asecond laterally adjacent pair of bone screw holes that is spacedlongitudinally from the first adjacent pair of bone screw holes.
 24. Thebone plate of claim 20, wherein the superior and inferior portions ofthe window extend longitudinally and the mid-portion of the windowextends transversely.
 25. The bone plate of claim 20, further comprisingrecessed areas adjacent to struts at superior and inferior ends of theplate, the recessed areas being formed in an outer periphery of theplate.
 26. The bone plate of claim 20, wherein the plate includes firstand second outer lateral sidewalls, wherein at least a portion of thefirst and second outer sidewalls adjacent to a bone screw hole iscurved.
 27. The bone plate of claim 20, wherein each of the plurality ofcams is integrated with the plate.
 28. The bone plate of claim 20,wherein the plurality of cams are aligned on the first and secondlongitudinal axes.
 29. The bone plate of claim 20, wherein each of theplurality of cams is configured to engage a bone screw disposed in abone screw hole adjacent to the cam when the cam is in the lockedposition.
 30. An implantable bone plate, comprising: an elongate platehaving superior and inferior ends; a first bone screw hole formed in theplate; a first locking cam disposed adjacent to the first bone screwhole and being rotatable with respect to the plate between a lockedposition and an unlocked position; a second bone screw hole formed inthe plate; a second locking cam disposed adjacent to the second bonescrew hole and being rotatable with respect to the plate between alocked position and an unlocked position; a third bone screw hole formedin the plate; a third locking cam disposed adjacent to the third bonescrew hole and being rotatable with respect to the plate between alocked position and an unlocked position; a fourth bone screw holeformed in the plate; a fourth locking cam disposed adjacent to thefourth bone screw hole and being rotatable with respect to the platebetween a locked position and an unlocked position; and a window formedin the plate; wherein the first and second bone screw holes are alignedon a first transverse axis of the plate; wherein the first and secondlocking cams are aligned on a second transverse axis of the plate thatis inferior to the first transverse axis; wherein the third and fourthlocking cams are aligned on a third transverse axis of the plate that isinferior to the second transverse axis; wherein the third and fourthbone screw holes are aligned on a fourth transverse axis of the platethat is inferior to the third transverse axis; wherein the first bonescrew hole and the third bone screw hole are aligned on a firstlongitudinal axis of the plate; wherein the second bone screw hole andthe fourth bone screw hole are aligned on a second longitudinal axis ofthe plate; wherein the window includes: a superior portion that extendssuperior to the second transverse axis; an inferior portion that extendsinferior to the third transverse axis; and a middle portion extendingbetween the superior and inferior portions and having a transversedimension that is greater than a transverse dimension of the superiorportion and a transverse dimension of the inferior portion.
 31. The boneplate of claim 30, wherein the inferior portion of the window includesopposed lateral sidewalls that are parallel to one another and whereinthe superior portion of the window includes opposed lateral sidewallsthat are parallel to one another.
 32. The bone plate of claim 30,further comprising a first stabilizing strut extending between the firstand second bone screw holes and a second stabilizing strut extendingbetween the third and fourth bone screw holes.
 33. The bone plate ofclaim 30, wherein: the superior sidewall of the superior portion of thewindow extends at least to a transverse bone screw hole plane extendingfrom an edge of the first bone screw hole to an edge of the second bonescrew hole; and the inferior sidewall of the inferior portion of thewindow extends at least to a transverse bone screw hole plane extendingfrom an edge of the third bone screw hole to an edge of the fourth bonescrew hole.
 34. The bone plate of claim 30, wherein the superior andinferior portions of the window extend longitudinally and the middleportion of the window extends transversely.
 35. The bone plate of claim30, further comprising recessed areas adjacent to struts at the superiorand inferior ends of the plate, the recessed areas being formed in theouter periphery of the plate.
 36. The bone plate of claim 30, whereinthe plate includes first and second outer lateral sidewalls, wherein atleast a portion of the first and second outer sidewalls adjacent to abone screw hole is curved.
 37. The bone plate of claim 30, wherein eachof the first, second, third, and fourth locking cams is integrated withthe plate.
 38. The bone plate of claim 30, wherein the first and thirdlocking cams are aligned on the first longitudinal axis and the secondand fourth locking cams are aligned on the second longitudinal axis. 39.The bone plate of claim 30, wherein the first, second, third, and fourthlocking cams are configured to engage respective bone screws disposed inthe first, second, third, and fourth bone screw holes, respectively,when said first, second, third, and fourth locking cams are in thelocked position.